This invention relates to a fuel supply system for the engine of an outboard motor and more particularly to an improved fuel control that will adjust the fuel delivery in response to a variety of engine running conditions and also in response to the trim of the outboard motor so as to provide stable running regardless of the engine parameters and trim angle adjustment.
The normal practice with outboard motors is to mount them on the transom of the associated watercraft for adjustment of the trim angle of the outboard motor and particularly its propulsion unit so as to provide optimum running under all conditions. Although the adjustment of the trim angle of the propulsion unit improves the efficiency of the propulsion unit, changes in the trim angle can adversely effect the running of the engine. For example, if the engine employs a carburetor, the adjustment of the trim angle can change the head between the fuel bowl and the discharge nozzle and can adversely effect the running of the engine.
Moreover, it has been found that the trim adjustment of the outboard motor can effect running even if only small trim changes are made. This is particularly true when the engine is running at slow speeds or with the throttle in a relatively closed position. At low speeds or low throttle openings, the flow through the induction passage is quite slow and the fuel tends to flow along the walls of the induction passage rather than being primarily vaporized centrally therein. This is true regardless of whether the engine is carbureted or has a fuel injection system. Depending upon whether the induction system is at the front or the rear of the engine, the trim angle can cause the engine to run either rich or lean as the trim is adjusted. This, of course, can provide uneven and undesirable running characteristics.
It is, therefore, a principal object of this invention to provide an improved fuel control system for an outboard motor wherein the running is optimized under all running conditions and trim conditions.
It is a further object of this invention to provide an improved fuel control for an outboard motor engine that is responsive both to engine running conditions and trim angle under substantially all circumstances.
It is a further object of this invention to provide an improved fuel supply system for an outboard motor so as to promote good running under all running conditions and under all trim conditions.
In addition to the steady state running of an engine, even the starting of an engine can be effected by the trim angle at which the outboard motor is positioned. Obviously, if the trim angle and location of the induction system is such that fuel tends to flow by gravity away from the combustion chambers rather than toward them, then the starting can be effected.
It is, therefore, a still further object of this invention to provide an improved arrangement for controlling the starting delivery of fuel to an engine in response to its trim condition.